1. Field of the Invention
The invention relates to golf balls with cores or intermediate layers prepared from melt-processable thermoplastic compositions comprising neutralized ethylene, C3 to C8 α,β ethylenically unsaturated carboxylic acid copolymers and organic acids.
2. Description of Related Art
Several patents and publications are cited in this description in order to more fully describe the state of the art to which this invention pertains. The entire disclosure of each of these patents and publications is incorporated by reference herein.
Premium golf balls include wound balls, two-piece balls and multilayered balls. Wound balls may have a spherical molded center, elastomeric thread-like material wound around the center, and either a thermoplastic or thermoset cover. Two-piece balls have a spherical molded core covered with a thin layer of thermoplastic or thermoset material. Multilayered balls have a spherical molded core, a cover, and one or more intermediate layers between the core and the cover.
Centers for wound balls and cores for two-piece and multi-layer balls have been made using a thermoset rubber such as polybutadiene rubber. With thermoset rubber, complex multi-step processes are needed to make cores and centers. These processes result in scrap that is difficult to recycle. Attempts to solve these difficulties by substituting a thermoplastic for the thermoset rubber have had limited success.
Thermoplastic ionomers of copolymers of alpha olefins, particularly ethylene, and C3-8 α,β ethylenically unsaturated carboxylic acids have found utility in golf ball components such as covers, and other applications. U.S. Pat. No. 3,264,272 teaches methods for making such ionomers. The acid copolymers on which the ionomers are based may be prepared as described in U.S. Pat. No. 4,351,931.
A wide range of cations is known for neutralizing acid moieties in the acid copolymer, including lithium, sodium, potassium, magnesium, calcium, barium, lead, tin, zinc, aluminum, and combinations of such cations and the degree of neutralization is known to vary over a wide range. Neutralization to 90% and higher, including up to 100%, is known, but such a high degree of neutralization can result in a loss of melt-processability or properties such as elongation and toughness. This is particularly so for copolymers with high acid levels.
U.S. Pat. Nos. 5,688,869; 6,150,470; 6,277,921; 6,433,094; 6,451,923; 6,573,335 and 6,800,695 disclose compositions, and golf ball covers comprising the compositions, comprising metal cation neutralized high acid ionomer resins comprising copolymers of greater than 16% by weight of an alpha, beta-unsaturated carboxylic acid and the balance an alpha-olefin, of which about 10 to about 90% of the carboxyl groups of the copolymer are neutralized with metal cations.
Ionomers have also been modified with fatty acids. For example, U.S. Pat. No. 6,777,472 discloses a thermoplastic composition that is melt-processable consisting essentially of (a) from 20 to 45 weight percent aliphatic, mono-functional organic acid(s) having fewer than 36 carbon atoms or salt(s) thereof; and (b) ethylene, C3 to C8 alpha,beta ethylenically unsaturated carboxylic acid copolymer(s) or melt-processable ionomer(s) thereof, wherein greater than 90% of all the acid of (a) and (b) is neutralized by concurrently or subsequently adding to the melt blend of (a) and (b) an amount of a cation source necessary to obtain greater than 90% neutralization.
Modified ionomers have been used as golf ball components. For example, U.S. Pat. No. 6,565,456 discloses multilayer golf balls comprising a solid core, a surrounding layer, an intermediate layer and a cover, wherein at least one of the surrounding layer, the intermediate layer or the cover is formed of a heated mixture comprising (a) an olefin-carboxylic acid-optional carboxylate random copolymer and/or (d) a metal ion-neutralized olefin-carboxylic acid-optional carboxylate random copolymer; (b) a fatty acid or derivative; and (c) a neutralizing basic inorganic metal compound.
U.S. Pat. No. 6,653,382 discloses golf balls comprising a thermoplastic polymer consisting essentially of at least one of (a) E/X/Y copolymers where E is ethylene, X is a C3 to C8 alpha,beta ethylenically unsaturated carboxylic acid, and Y is a softening co-monomer of the E/X/Y copolymers, wherein X is about 3-30 weight % of the E/X/Y copolymer, or partially neutralized ionomers thereof, and Y is about 0-30 weight % of the E/X/Y copolymer; and (b) one or more aliphatic, mono-functional organic acids having fewer than 36 carbon atoms or salts thereof being present in the range of about 25 to about 150 parts per hundred parts by weight of the E/X/Y copolymer, wherein greater than 90% of all the acid of (a) and of (b) is neutralized with a cation source.
US Patent Application Publication 2002/0111407 discloses golf balls comprising a base resin comprising a (metal ion-neutralized) olefin-unsaturated carboxylic acid-unsaturated carboxylate ternary random copolymer and optionally a (metal ion-neutralized) olefin-unsaturated carboxylic acid binary random copolymer blended with specific proportions of a fatty acid and/or fatty acid derivative and a basic inorganic metal compound capable of neutralizing acidic groups left unneutralized in the base resin and fatty acid.
U.S. Pat. No. 6,953,820 discloses a composition, and golf balls comprising the composition, comprising a thermoplastic polymer blend which has a coefficient of restitution of at least 0.785 and an Atti compression of no more than 100, wherein the blend consists essentially of at least one (a) E/X/Y copolymers where E is ethylene, X is a mixture of at least two C3 to C8 alpha,beta ethylenically unsaturated carboxylic acids, and Y is a softening comonomer or ionomers of the E/X/Y copolymers wherein X is about 3-30 weight % of the E/X/Y copolymer, and Y is 0 to about 30 weight % of the E/X/Y copolymer; and (b) one or more aliphatic, mono-functional organic acids having fewer than 36 carbon atoms or salts thereof, wherein greater than 90% of all the acid of (a) and of (b) is neutralized.
It is desirable to provide a high performance material to be used in the cores, centers or intermediate layers of golf balls.